Central venous catheters typically stimulate intravascular coagulation, which occasionally progresses to occlusive deep vein thrombosis. In an attempt to prevent this, we have explored the possibility of coating silicone catheters with a new anticoagulant, lepirudin, which because it is a protein has a natural tendency to adsorb to polymeric surfaces. We have shown that lepirudin adsorbed to silicone retains much of its anti-thrombin activity and that the drug is only partially displaced by plasma proteins. Therefore, it may be effective in reducing the incidence of thrombosis associated with these catheters.